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AR# 57193: Design Advisory for Artix-7, Kintex-7, Virtex-7, Zynq-7000 Packaging - The 7 Series Thermal Resistance Values (Theta-JA, Theta-JB, and Theta-JC) are being updated with more accurate values, many of which are substantially changed

AR# 57193

Design Advisory for Artix-7, Kintex-7, Virtex-7, Zynq-7000 Packaging - The 7 Series Thermal Resistance Values (Theta-JA, Theta-JB, and Theta-JC) are being updated with more accurate values, many of which are substantially changed

Description

The thermal resistance values for Theta-JA, Theta-JB, and Theta-JC are being updated for the Zynq-7000, Artix-7, Kintex-7, and Virtex-7 family devices. For many packages, the thermal resistance numbers will increase, adversely impacting thermal dissipation estimates. These incorrect values are also propagated through the Xilinx Power Estimator Spreadsheet (XPE) prior to 2013.3, so customers who leveraged this tool to estimate thermal aspects of power dissipation will be impacted.

Solution

For many 7 series devices (Artix-7, Kintex-7, Virtex-7, and Zynq-7000 familes), the thermal resistance values (Theta-JA, Theta-JB, and Theta-JC) were incorrectly extracted and were documented with inaccurate values. Updated thermal resistance values have been released and are documented starting in version 1.10 of the 7 Series Packaging and Pinout Product Specification User Guide (UG475), version 1.3 of the Zynq-7000 All Programmable SoC Packaging and Pinout Product Specification User Guide (UG865), the thermal lookup tool (after 8/26/2013): http://www.xilinx.com/cgi-bin/thermal/thermal.pl, and the 2013.3 Xilinx Power Estimator Spreadsheet (XPE).

For customers who leverage thermal resistance values to model the thermal performance of their system, it is recommended that thermal analysis is re-run with the updated thermal resistance numbers.

Customers who analyzed their system with Delphi-format compact thermal models are not required to re-analyze their system, as that model is not impacted by this issue.

Xilinx generates three different thermal models:

Detailed 3-D Flotherm model

Not generally distributed to customers

Validated with thermal measurements

Used to validate Delphi and 2-resistor models

Delphi-format model

Distributed to customers

No errors in this model for 7 series devices

Derived from the Detailed 3-D model

2-resistor model

Distributed to customers

Theta J values published in user guide

This model and Theta values are erroneous

Thermal resistance numbers are primarily used to estimate the heat dissipation of a system:

Theta-JC (JC) measures the heat flow resistance between the die surface and the surface of the package (case). Theta-JC is used primarily in estimating heat dissipation in a system that leverages a heat sink or other method beyond the device package.

Theta-JA (JA) measures the heat flow resistance between the die surface and ambient. Theta-JA is often used to estimate the junction temperature that will result when estimating the power that an IC will consume in a system with just the IC and a environment specified by JEDEC.

Theta-JB (JA) measures the heat flow resistance between the die surface and the Printed Circuit Board.

The following tables quantify the percentage change to the thermal numbers compared to previously published values (negative % changes represent an improved thermal resistance value).